Post on 19-Dec-2015
description
1Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Telecommunication Networks
Dr. Ing. Vo Que Son
Email: sonvq@hcmut.edu.vn
2Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Chapter 5: MPLS NetworksMPLS
DiffServ in MPLS
MPLS TE
FATE schemes
Chapter 6: Traffic EngineeringM/M/1, M/M/c models
M/G/1, M/D/1 models
Queuing networks
Application of queuing theory in Network QoS
Content
3Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Internet core network
Router based core network
4Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Internet core network (cont)
Processing can not meet bandwidth demands
Bottle-neck in software-based routers
Available router interfaces not provide traffic aggregation
Metric-based routing was no longer scalable
Densely connected networks lead to inefficient use of network resources
Destination based routing tends to aggregate all traffic to the same destination: not utilize links
5Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Internet core network (cont)
Switch based core network
6Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Internet core network (cont) Faster and simpler forwarding, better traffic aggregation
Fix size cells can be handled in hardware to speed up
Connection-oriented forwarding algorithm improves performance gain: based on short fix length connection identifiers
The ASIC technology : IP packets can be forwarded with high speed. ATM interfaces have even fallen behind the latest increases of optical network (packet over SDH/SONET)
Waste of bandwidth : 5/48 bytes of header.
Complex network management: physical ATM switched infrastructure and logical IP network topology. Each layer uses its own addressing scheme and routing protocol
7Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Internet core network (cont)
The n-squared problem : when adding or shutting down any router will create enormous signaling load
IGP stress : intra-domain routing is not conceived for fully meshed topology. With high number of routing peer routers: too much routing information has to be exchanged
Multi-Protocol Label Switching (MPLS) can offer solutions that create a combination of the advantages from both of these worlds
8Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS NGN
9Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS NGN (cont)
Forwarding based on label: speed up processing at node
Forwarding mechanism: label (explicit routing) or IP header (hop-by-hop routing)
Operating on any layer 2 technologies: ATM, Ethernet, FR
Allows for both traffic aggregation and disaggregation
Support VPN : using 64-bit VPN address (total 92 bits)
Allow SPs embed into the IP network : TE and traditional QoSof layer 2 : using DSCP and processing queues based on its packets priority
Easy management and operation
10Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Traditional IP Routing
Choosing the next hopOpen Shortest Path First (OSPF) to populate the routing
table
Route look up based on the IP address
Find the next router to which the packet has to be sent
Replace the layer 2 address
Each router performs these steps
11Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Traditional IP Routing (contd)
12Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Distributing Routing Information
You can reach 145.40 through me
You can reach 125.50 through me
You can reach 125.50 and 145.40 through me
3
1
0125.50
145.40
2
AddressPrefix
AddressPrefix
AddressPrefix
Path Path
Path
125.50
145.40
125.50
145.40
125.50
13
3 0
2
13Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Distributing Routing Information(contd)
3
1
0125.50
145.40
2
AddressPrefix
AddressPrefix
AddressPrefix
Path Path
Path
125.50
145.40
125.50
145.40
125.50
13
3 0
2
Data 125.50.33.85
Data 125.50.33.85
14Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Disadvantages
Header analysis performed at each hop
Increased demand on routers
Utilizes the best available path
Some congested links and some underutilized links!
Degradation of throughput
Long delays
More losses
No QoS
No service differentiation
Not possible with connectionless protocols
15Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Need for MPLS
Rapid growth of Internet
New latency dependent applications
Quality of Service (QoS)
Less time at the routers
Traffic Engineering
Flexibility in routing packets
Connection-oriented forwarding techniques with connectionless IP
Utilizes the IP header information to maintain interoperability with IP based networks
Decides on the path of a packet before sending it
16Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
What is MPLS? Multi Protocol supports protocols even other than IP
Supports IPv4, IPv6, IPX, AppleTalk at the network layer
Supports Ethernet, Token Ring, FDDI, ATM, Frame Relay, PPP at the link layer
Label short fixed length identifier to determine a route
Labels are added to the top of the IP packet
Labels are assigned when the packet enters the MPLS domain
Switching forwarding a packet
Packets are forwarded based on the label value
NOT on the basis of IP header information
17Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS Background Integration of layer 2 and layer 3
Simplified connection-oriented forwarding of layer 2
Flexibility and scalability of layer 3 routing
MPLS does not replace IP; it supplements IP
Traffic can be marked, classified and explicitly routed
QoS can be achieved through MPLS
18Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
IP/MPLS comparison
Routing decisions
IP routing based on destination IP address
Label switching based on labels
Entire IP header analysis
IP routing performed at each hop of the packets path in the network
Label switching performed only at the ingress router
Support for unicast and multicast data
IP routing requires special multicast routing and forwarding algorithms
Label switching requires only one forwarding algorithm
19Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Key Acronyms
MPLS MultiProtocol Label Switching
FEC Forward Equivalence Class
LER Label Edge Router
LSR Label Switching Router
LIB Label Information Base
LSP Label Switched Path
LDP Label Distribution Protocol
20Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Forwarding Equivalence Class (FEC)
A group of packets that require the same forwarding treatment across the same path
Packets are grouped based on any of the following Address prefix
Host address
Quality of Service (QoS)
FEC is encoded as the label
21Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FEC example
Assume packets have the destination address as
124.48.45.20
143.67.25.77
143.67.84.22
124.48.66.90
FEC 1 label x FEC 2 label y
143.67.25.77 124.48.45.20
143.67.84.22 124.48.66.90
22Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FEC example (contd)
- Assume packets have the destination address and QoS requirements as
124.48.45.20 qos = 1
143.67.25.77 qos = 1
143.67.84.22 qos = 3
124.48.66.90 qos = 4
143.67.12.01 qos = 3
FEC 1 label a FEC 2 label b FEC 3 label c FEC 4 label d
143.67.25.77 124.48.45.20 143.67.84.22 124.48.66.90
143.67.12.01
23Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Example of a MPLS network
24Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label Edge Router (LER)
Can be an ATM switch or a router
Ingress LER performs the following: Receives the packet
Adds label
Forwards the packet into the MPLS domain
Egress LER removes the label and delivers the packet
25Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label Switching Router (LSR)
A router/switch that supports MPLS
Can be a router
Can be an ATM switch + label switch controller
Label swapping Each LSR examines the label on top of the stack
Uses the Label Information Base (LIB) to decide the outgoing path and the outgoing label
Removes the old label and attaches the new label
Forwards the packet on the predetermined path
26Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label Switching Router (contd)
Upstream Router (Ru) router that sends packets
Downstream Router(Rd) router that receives packets
Need not be an end router
Rd for one link can be the Ru for the other
Ru Rd Ru Rd
27Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label Switched Path(LSP)
LSP defines the path through LSRs from ingress to egress router
FEC is determined at the LER-ingress
LSPs are unidirectional
LSP might deviate from the IGP shortest path
28Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
LSP
LSP
Label Switched Path(LSP)
29Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Shim Header A short, fixed length identifier (32 bits)
Sent with each packet
Local between two routers
Can have different labels if entering from different routers
One label for one FEC
Decided by the downstream router
LSR binds a label to an FEC
It then informs the upstream LSR of the binding
30Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Shim Header (contd) EXP field
Also known as Class of Service (CoS) bits
Used for experimentation to indicate packets treatment
Queuing as well as scheduling
Different packets can receive different treatment depending on the CoS value
S bit Supports hierarchical label stack
1 if the label is the bottom most label in the label stack
0 for all other labels
31Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Time To Live (TTL) TTL value decremented by 1 when it passes through an LSR
If TTL value = 0 before the destination, discard the packet
Avoids loops may exist because of some misconfigurations
Multicast scoping limit the scope of a packet
Supporting the traceroute command
32Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
TTL (contd)
Shim header
Has an explicit TTL field
Initially loaded from the IP header TTL field
At the egress LER, value of TTL is copied into the TTL field of the IP header
Data link layer header (e.g VPI/VCI)
No explicit TTL field
Ingress LER estimates the LSP length
Decrements the TTL count by the LSP length
If initial count of TTL less than the LSP length, discard the packet
33Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label: AToM ATM
VCI/VPI field of ATM header
Frame Relay
DLCI field of FR header
PPP/LAN
shim header inserted between layer 2 and layer 3
34Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label stack
MPLS supports hierarchy
A packet can carry a number of labels
Each LSR processes the topmost label Irrespective of the level of hierarchy
If traffic crosses several networks, it can be tunneled across them
Use stacked labels
Advantage reduces the LIB table of each router drastically
35Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label stack (contd)
36Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label stack (contd)
37Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Labels scope and uniquenessLabels are local between two LSRs
Rd might give label L1 for FEC F and distribute it to Ru1
At the same time, it might give a label L2 to FEC F and distribute it to Ru2
L1 might not necessarily be equal to L2
Can there be a same label for different FECs? Generally, NO
BUT no such specification
LSR must have different label spaces to accommodate both
SHIM header specifies that different label spaces used for unicast packets and multicast packets
38Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Invalid labelsWhat should be done if an LSR receives an invalid
label?
Should it be forwarded as an unlabeled IP packet?
Should it be discarded?
MUST be discarded!
Forwarding it can cause a loop
Same treatment if there is no valid outgoing label
39Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Route selectionRefers to the method of selecting an LSP for a
particular FEC
Done by LDP Set of procedures and messages
Messages exchanged between LSRs to establish an LSP
LSRs associate an FEC with each LSP created
Two types of LDP Hop by hop routing
Explicit routing
40Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Route selection (contd)Hop by Hop
Allows each LSR to individually choose the next hop
This is the usual mode today in existing IP networks
No overhead processing as compared to IP
Explicit routing A single router, generally the ingress LER,specifies several
or all of the LSRs in the LSP
Provides functionality for traffic engineering and QoSo Several: loosely explicitly routed
o All: strictly explicitly routed
E.g. CR-LDP, TE-RSVP
41Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Label Information Base (LIB)Table maintained by the LSRs
Contents of the table Incoming label
Outgoing label
Outgoing path
Address prefix Incoming label Address PrefixOutgoing
Path
Outgoing
label
42Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS forwarding
Existing routing protocols establish routes
LDP establishes label to route mappings
LDP creates LIB entries for each LSR
Ingress LER receives packet,adds a label
LSRs forward labeled packets using label swapping
Egress LER removes the label and delivers the packet
43Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FEC in MPLS
44Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS forwarding (contd)
Use label 8 for 145.40
Use label 9 for 125.50
Use label 2 for 125.50 andlabel 1 for 145.40
3
1
0125.50
145.40
2
AddressPrefix
AddressPrefix
Out Path
In Label
Out Path
Out Path
In Label
In Label
Out Label
Out Label
Out Label
125.50 125.50
125.50
145.40 145.40
3
3
2
1
2
1 8
9
9
0
1
2Address
Prefix
45Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS forwarding (contd)
3
1
0125.50
145.40
2
AddressPrefix
AddressPrefix
AddressPrefix
Out Path
In Label
Out Path
Out Path
In Label
In Label
Out Label
Out Label
Out Label
125.50 125.50
125.50
145.40 145.40
3
3
2
1
2
1 8
9
9
0
1
2
Data 125.50.33.85 2
Data 125.50.33.85 9
46Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
DiffServ & MPLS
46
47Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
DiffServ Architecture
48Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
The IETF DiffServ ModelUse 6 bits in IP header to sort traffic into
Behavior AggregatesAKA Classes!
Defines a number of Per Hop Behaviors - PHBs Two-Ingredient Recipe:
Condition the Traffic at the Edges
Invoke the PHBs in the Core
Use PHBs to Construct Services such as Virtual Leased Line!
49Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Defined PHBs
Expedited Forwarding (EF): RFC2598 dedicated low delay queue Comparable to Guaranteed B/W in IntServ
Assured Forwarding (AF): RFC25974 queues 3 drop preferencesComparable to Controlled Load in IntServ
Class Selector: Compat. with IP PrecDefault (best effort)
50Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
AF PHB Group Definition
4 independently-forwarded AF classes
Within each AF class, 3 levels of drop priority! This is very useful to protect conforming to a purchased, guarantee rate, while increasing chances of packets exceeding contracted rate being dropped if congestion is experienced in the core.
AF Class 1: 001dd0
AF Class 2: 010dd0
AF Class 3: 011dd0
AF Class 4: 100dd0
Eg. AF12 = Class 1, Drop 2, thus 001100
dd = drop preference
51Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
DiffServ Scalability via Aggregation
DiffServ scalability comes from:- aggregation of traffic on Edge- processing of Aggregate only in Core
1000s of flows
Diff-Serv:
Aggregated Processing in Core
Scheduling/Dropping (PHB) based on DSCP
Diff-Serv:
Aggregation on Edge
Many flows associated with a Class (marked with DSCP)
52Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS Scalability via Aggregation
MPLS scalability comes from:- aggregation of traffic on Edge- processing of Aggregate only in Core
1000s of flows
MPLS:
Aggregated Processing in Core
Forwarding based on label
MPLS:
Aggregation on Edge
Many flows associated with a Forwarding Equivalent Class (marked with label)
53Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS & DiffServ - The Perfect Match!
Because of same scalability goals, both models do:- aggregation of traffic on Edge- processing of Aggregate only in Core
1000s of flows
MPLS: flows associated with FEC, mapped into one label
MPLS: Switching based on Label
DS: Scheduling/Dropping based on DSCP
DS: flows associated with Class, mapped to DSCP
54Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
DSCP field is not directly visible to MPLS Label Switch Routers (they forward based on MPLS Header)
Information on DiffServ must be made visible to LSR in MPLS Header (using EXP field / Label)
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label | EXP |S| TTL |
DSCP
IPv4 Packet MPLS Header
Non-MPLS Diff-Serv Domain
MPLS Diff-Serv Domain
DSCP
MPLS:Whats New? The Shim Header
55Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
DS o MPLS : Coloring MPLS Frames
This describes how DiffServ information is conveyed to LSRs in MPLS Header
Two methods: E-LSP {{ Cisco IOS 12.1(5)T, 12.0(11)ST }}
Queue inferred from Label and EXP fieldDrop priority inferred from label and EXP
field
L-LSP {{ Planned, once an RFC }}Queue inferred exclusively from Label Drop priority inferred from EXP field
56Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
E-LSPs can be established by various label binding protocols (LDP or RSVP)no new Signalling Needed.
Example above illustrates support of EF and AF1 on a single E-LSP (Note: This is the plain old LSP established for MPLS Switching)
Note: EF and AF1 packets travel on single LSP (single label) but are enqueued in different queues (different EXP values)
Queue & Drop Precedence is selected based on EXP
E-LSP
LSRLDP/RSVP LDP/RSVP
EF
AF1
The E-LSP Story...
57Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
L-LSPs can be established by various label binding protocols (LDP or RSVP)EXTENSIONS REQUIRED!
Example above illustrates support of EF and AF1 on separate L-LSPs
EF and AF1 packets travel on separate LSPs and are enqueued in different queues (different label values)
Queue selected based on Label, Drop Precedence Selected with Optional EXP field.
L-LSPs
LSR
LDP/RSVP LDP/RSVP
L- LSP Supporting 64 Classes!
58Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS Traffic Engineering
58
59Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
The Fish ProblemR8
R1
R5
R2
R3R4
R7R6
IP Uses Shortest Path Destination-Based Routing
Shortest Path May Not Be the only path Alternate Paths May Be under-Utilized while the
shortest Path Is over-Utilized
60Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
An LSP Tunnel: (A Constrained MPLS LSP)
R8
R1
R5
R2
R3R4
R7R6
Labels, Like VCIs (ATM) Can Be Used to Establish Virtual Circuits
Normal Route R1->R2->R3->R4->R5
Tunnel: R1->R2->R6->R7->R4
61Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
LSP Tunnel Setup
22
4917
R8
R2
R6
R3
R4
R7
R1R5
R9
Setup: Path (R1->R2->R6->R7->R4->R9) Tunnel ID 5, Path ID 1
Reply: Communicates Labels and Label OperationsReserves Bandwidth on Each Link
Pop
32
62Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Real-World MPLS TE Use!
POP4
POP
POPPOP
POP2
POP1
WAN area
Find route & set-up tunnel for 10 Mb/s from POP2 to POP4
Find route & set-up tunnel for 20 Mb/s from POP1 to POP4
63Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
MPLS TE & QoS The Relationship
MPLS TE designed as tool to improve backbone efficiency independently of core QoS techniques: MPLS TE compute routes for aggregates across all PHBs.
A Single Chunk of Bandwidth requested for the Tunnel
MPLS TE performs admission control over a global b/w pool. Un-aware of bandwidth allocated to each Class / PHB
MPLS TE and MPLS DiffServ: Can run simultaneously in a network. Can provide their own individual benefits
TE distributes aggregate load
DiffServ provides differentiation)
Are unaware of each other
64Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
LDP: Label Distribution Protocol
Label Distribution Protocol
65Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
LDP
66Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Traffic Aggregate in IP networks
67Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Traffic Aggregate in MPLS networks
68Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Traffic Aggregate in MPLS networks
69Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
TE Fast Reroute - Tunneling
70Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
TE Global Fast Reroute (Makam)
71Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
TE Region Fast Reroute
72Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
TE Local Fast Reroute
73Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
TE Haskin Fast Reroute
74Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
LDP - Advantages Explicit routing
Set up a LSP between Ingress Router and Egress Router
Label request for each hop on down-stream
Label mapping : up-stream
Errors occur: router sends a alarm message to neighbors or operating routers to re-direct for current LSP
Less resources (compared with RSVP)
75Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
LDP - Disadvantages Slow error recovery
Not support dynamically re-optimization of traffic flows
Transient periods: efficiency of Resource Location could be influenced by routing traffic.
Require means to restore the LSP to the original routes once congestion has subsided
FATE, FATE+ : using dynamic reroute mechanism
FATE++ : combination of 2 above algorithms with improvements
76Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
Weighted Fair Queue Monitoring packets
Classifier
10-6
10-4
Scheduler
Output linkIP LIP L
IP L
Input link
IP L
Output buffer
Unsuccessful insertion. Destroy packet.
Successfully inserted packets
per-class buffering
Template
Management
CCCDCCCDCCCD
Buffer ID
C
D
77Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE - Fast Acting Traffic Engineering
At each LSR:
If packet loss: calculate packet loss in buffer
If this over pre-defined threshold, generate a Congestion Indicator (CIN) message to Ingress Router on upstream
Set up a timer for CIN regeneration
CIN: Congestion Indication Notification
78Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE Mechanism (cont)
At other LSRs on up-stream: when receiving CIN
If timer not expired, forward CIN without appending infor
Otherwise, add its congested info before forwarding
At Ingress LSR: when receiving CIN message
Decide that the packet loss it is currently experiencing remains sufficiently low for it to continue to meet its SLA requirements, allowing no further action to be taken
Renegotiate for a new requirements along existing LSP (higher priority buffer along same path, within same LSR)
Negotiate for a new quality requirements along an alternative LSP
79Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE CIN information
Identity of the LSP that is experiencing congestion
The LSRs this loss is occurring in
The current loss in the buffers the LSP is traversing
The current loss of the LSP
80Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE Scalability
How to monitor thousands of LSPs ?
How a MPLS network applies congestion control mechanism in a situation of numerous flows?
How can SPs ensure the customers SLA is met while traversing this network?
Solutions
In a single domain: exchanging messages can be easily handled under the control of Ingress and Egress LERs
In a Generalized MPLS domain : assign Virtual Source/Virtual Destination (VS/VD) of each domain using label stacking
81Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE Label stacking
82Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE Advantages/Disadvantages Fast acting mechanism
Allow individual LSPs to be dynamically remapped to QoS buffers
Provide a notification from congested LSR to Ingress LER
Can not make decision about the current LSP
Suitable in strictly routed LSPs
83Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE+ - Extension of FATE Remove generation of CIN message
Redistributing traffic flows while fully utilizing all available LSRs and links
Ensure the customers SLAs are met
Suitable in loosely routed LSPs
Scale well in large WANs
Permit the congested LSR to make decisions :
Transfer the CR-LSP on to a higher buffer stream
Re-route the CR-LSP via an alternative downstream LSR
Re-route the CR-LSP via an alternative upstream LSR
84Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE+ - Transfer LSP to a higher buffer stream
85Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE+ - Reroute via a alternative downstream LSR
86Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE+ - Reroute via a alternative upstream LSR
87Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE+ - Disadvantages
Loop packets
Can not reroute when:
Finding a new LSP via downstream LER but no resources
Congested LER and its neighbors can not reroute but other LERs can
88Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE+ - Loop packets
89Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE+ - No resources
90Telecomm. Dept.Faculty of EEE
Telecom NetworksHCMUT
FATE++ - Dual FATE and FATE+